The invention deals with a system for the improvement of loom efficiency, the comfort and the hygienic conditions within the weaving room and for the reduction of the energy needed for the conditioning of the air in the weaving room. These goals are obtained by precisely controlling the moisture content of the yarn being fed into each loom by removing solids and heat generated by the weaving process at their source, and by improving the handling of the air in the weaving room.
Woven fabrics are made up by combining warp yarn (lengthwise) with filling yarn (widthwise), in such a way as to obtain the desired look and strength of the fabric.
Warp beams, containing the necessary number of ends, are fed into the loom (weaving machine). Please see FIG. 1, item [1]. Every end is conducted through a break detector [2], by which the machine is stopped in case of a warp break.
The ends are risen and lowered by the heddles [4] forming the shed [3]. The filling yarn [5] is inserted within the shed and pressed by the reed [6] towards the exiting fabric [7].
Loom speed has increased over the time from a few picks per minute (ppm) to about 1000 presently. By the yarn movement in the shed, warp yarns are subjected to very frequent tensioning and yarn-to-yarn abrasion. To prevent warp breaks, said yarn should have: high tensile strength and elasticity, no weak points nor adhering in fiber bundles (slubs), very low hairiness.
An adequate yarn humidity is needed to enhance the strength and the elasticity and to smoothen the yarn surface.
The following descriptions and statements are especially valid for products made up by natural fibers and their blends with synthetic and artificial fibers.
Both tensile strength and elasticity depend on fiber and spinning characteristics, on warp pretreatment (slashing) and increase with moisture content of the yarn being fed into the weaving process.
Hairiness depends on the spinning system and the fiber quality. It is reduced by slashing, as fibers protruding from the yarn are glued to it. Moisture content smoothens the hairs and lubricates the yarn surface.
Abrasion between yarns, mainly in the shed area, removes short fibers (lint) and size dust from the warp yarn. Adequate yarn moisture reduces the fall out.
While the weaving process is performed, the following interactions occur: The yarn adsorbs water from the air. Lint and dust falling out from the yarn are incorporated into the room air. Power consumed by the loom and other devices in the room is converted into heat and incorporated into the room air.
Experience shows that yarns perform best in weaving machines when their humidity is 7-9% (parts of water in 100 parts of dry yarn). Less humidity reduces strength, elasticity and smoothness. Higher moisture may make the size glue the warp yarns together.
Historically weaving mills were located in cool damp areas, looms run at a fraction of present speeds, and the yarn was stored for weeks inside the weaving room. When the mills were relocated to warmer and dryer climates, air conditioning systems were installed, in order to replicate the former conditions.
Yarn exposed to humid air adsorbs water, and after several hours, reaches an equilibrium. Present high-speed looms expose the yarn (especially the warp) for just a few minutes to the room air. This time is not long enough to obtain an adequate humidity level on the yarn.
In lab tests conducted with cotton yarns, the following yarn moistures have been measured before and after exposing it to air held at 25xc2x0 C.:
Warp yarns usually are dried by the slashers to 5-6% moisture. But during stops, part of the yarn is grossly over dried to 1-2% moisture. Most warp yarn breaks are concentrated in these parts.
Filling yarn moisture falls within the 3-7% range, depending mainly on the spinning technology employed. Sometimes yarn conditioning prior to weaving is required.
Yarn exposure to the room air during the weaving process is as short as 15 minutes or less. As shown in the tables above, by present methods, the weaving process would run best with a very high room humidity level, in the 85-95% range.
But operator comfort imposes a limit, usually 70-75%. Room temperature is frequently kept within the 24-26xc2x0 C. range.
Recently two companies (LUWA-Bahnson and LTG Air Engineering) introduced systems projecting cool nearly saturated air from about 1500 mm over the shed on the yarn. Better loom performance has been reported.
Observations made in several cotton mills showed that solids fall-out has the following distribution:
In modem weaving mills, contaminated air is usually returned to the AC, located outside of the room, through openings under the looms. Solids are removed by filtration and/or water sprayed into the air stream. As an important part of the solids in the room are carried upward by the heat generated by the looms, only about 30-40% of the total fall out is captured by this system.
In order to keep the shed, the upper part of the weaving machines, and floor lint free, a device usually described as xe2x80x9ctraveling cleanerxe2x80x9d moves along several machines, periodically blowing solids away from those parts and vacuuming off another 25-30% of the total.
The remainder of the lint and dust is moved by air turbulence all over the room and clings to the machines, the ducts, the light fixtures, the ceiling, and the walls. Its removal has to be performed by hand.
Increased machine speed requires a high power input (4-8 kw per loom). This energy is totally converted into heat and dissipated into the room air. The already mentioned traveling cleaners and the illumination also add to the room heat load. As the air heat capacity is very low, huge volumes of air have to be carried by the AC system from and back to the loom area.
Relatively large areas of the weaving room (each occupied by 40-120 looms) are served by each AC system, consisting of several openings under each loom, through which contaminated air is returned by underground air ducts to the AC unit. Within said AC unit, the air is filtered, sprayed with chilled water, cooled, and humidified to 95-97%, and finally propelled by fans through overhead ducts, to be uniformly distributed over the area served.
Provisions are made to replace returned air by fresh outside air, when external conditions are favorable. The chilled water mentioned above usually is cooled by compressors.
Relevant prior art includes Shofner U.S. Pat. Nos. 5,676,177 and 5,910,598, Chern U.S. Pat. No. 4,966,017 and Vignoni U.S. Pat. No. 5,275,350.
Shofner U.S. Pat. Nos. 5,676,177 and 5,910,598 deal mainly with the elimination of solids from the shed with devices that are bulky and very difficult to locate in an operating weaving machine, also interfering with the operator, while the blowers add heat to the air, thereby drying the yarn.
Chern U.S. Pat. No. 4,966,017 discloses a method and apparatus for moistening creels feeding other machines.
Vignoni U.S. Pat. No. 5,275,350 discloses a device to improve creel-operating conditions wherein the air is received and goes back to a centralized generator.
Shofner U.S. Pat. No. 5,910,598, although also discloses a room environmental improvement, has different ways of obtaining it regarding solid and heat removal with respect of present invention.
The following descriptions and statements are especially valid for products made up by natural fibers and their blends with synthetic and artificial fibers.
Tensile strength: Depends on fiber and spinning characteristics, on warp pretreatment (slashing) and on moisture content of the yarn being fed into the weaving machine.
Elasticity: Natural fibers elasticity increases with their moisture content.
Hairiness: Depends mainly on the spinning system. Is reduced by slashing, as fibers protruding from the yarn are glued to it. Yarn moisture content smoothens the hairs.
Lint and dust fall out: Abrasion between yarns, mainly in the shed area, removes short fibers (lint) and size dust from the warp yarn. Adequate yarn moisture reduces the fall out.
Yarn humidity (moisture): As seen above, an adequate humidity level on the yarn improves its performance in the weaving process.
In brief, the system of the invention comprises four subsystems. Each of the subsystems performing a definite task separately.
Subsystems are:
[A] The necessary moisture required by the yarn to perform best in the loom is metered exactly and directly on the yarn. Thereby, yarn breakage is reduced and weaving room air humidity can be lowered, thereby improving human comfort.
[B] Lint and dust generated by the weaving process are removed at their source. Air contamination is lowered, thereby improving hygienic conditions and reducing air filtration requirements and making traveling cleaners unnecessary.
[C] Heat generated by the weaving process is partly removed by water-cooling the lubricating oil of the weaving machine, thereby reducing the weaving room heat load.
[D] Large peripherally located air conditioning units are replaced by smaller units, distributed over or under the roof of the room, each serving the area of 4-24 looms. Due to subsystems [A, B, C], filtration and cooling requirements are greatly reduced. Air humidification is not needed. The fan and coil conditioning system is best suited for this application.
Subsystems [A, B, C] are operated on each loom separately, thereby increasing production flexibility. Loom efficiency is increased as yarn breaks are lowered to less than half.
Conditioned air will be projected on the aisles of work place. Room air will be collected for recycling at a higher level. Thereby turbulences, usually produced by ascending warm air, are prevented. Under floor air ducts are no longer necessary.
Due to subsystems A, B, C, less air will have to be turned over. Due to decentralization of AC units, said air will be transported over shorter distances. Thereby, substantial amounts of energy are saved.
By subsystem D, lesser air ducts are needed, thereby reducing investment costs. By elimination of under ground ducts and openings in the floor, replacement or rearrangement of weaving machines is made easier.